'Mental defectives' were the responsibility of different sections of the Victorian government at different points in time. From the nineteenth century, the Hospitals for the Insane Branch within the Chief Secretary's Department, and later the Lunacy Department were responsible for the 'care' of children and adults defined, using the language of the time, as 'idiots'.

As early as 1913, the Department of Education established special schools for children. In 1934, responsibility shifted from education to the new Department for Mental Hygiene. By the mid 1940s, 'mental hygiene' was seen to be a health issue and the Mental Hygiene Branch was established within the new Victorian Department of Health.

The Mental Deficiency Act 1939 contained the following definition of 'mental defectiveness':

'Mental defectiveness means a condition of arrested or incomplete development of mind existing from birth or from an early age whether arising from inherent causes or induced by disease or injury and of such a kind as to render the person affected incapable of adjusting himself to his social environments and as to necessitate external care, supervision, or control of such person.'

In an address given in 1940, Dr Guy Springthorpe discussed the further classification of 'mental defectives' under the legislation:

(a) Imbeciles; that is to say persons in whose case there exists mental defectiveness which is so pronounced that they are incapable of managing themselves or their affairs or, in the case of children, of being taught to do so;

(b) Feeble-minded persons; that is to say persons not less than sixteen years of age in whose case there exists mental defectiveness which though not amounting to imbecility is yet so pronounced that they require care, supervision and control for their own protection or for the protection of others ;

(c) Moral defectives; that is to say persons not less than sixteen years of age in whose case there exists mental defectiveness coupled with strongly vicious or criminal propensities, and who require care, supervision and control for their own protection or for the protection of others.

Springthorpe went on to explain another definition, that of the 'retarded child':

'a person under sixteen years of age in whose case there exists mental retardation which though not amounting to imbecility is yet so pronounced that he may become a feeble-minded person and who appears to be permanently incapable by reason of such mental retardation of receiving proper benefit from the instruction given in ordinary schools.'

In 1940s Australia, some commentators, influenced by ideas of eugenics [selective breeding], questioned the wisdom of Victorian government initiatives like the Mental Deficiency Act 1939. For example, Judge Foster remarked at a meeting of the Medico Legal Society in 1940:

'There are a number of slum children, who might be called economically defective, who would envy the children shown, and I make a confident assertion that there are few children in our poorer suburbs on whom is spent anything like the £70 or £80 a year that is spent on people in these institutions. It would be a very proper thing for the community to look after not only the mentally defective but the economically defective in their midst. Then what of the eugenic aspect? Are we, by making mentally retarded persons into useful citizens who may propagate their kind, tending gradually to lower the intellectual standards of society? My reading leads me to fear that this may be the case. If so, we may yet have to face the problem of sterilization, which has been faced in the United States and in Germany.'

Springthorpe described the common situation for 'mentally defective' children in Victoria in 1940. Despite the existence of the Department of Mental Hygiene, large numbers of children were being accommodated in inappropriate children's institutions run privately, or by the Children's Welfare Department. Springthorpe cited an investigation in 1939 which had found that 'on any one day at the Welfare Depot [Royal Park] 30 per cent of the residents were mentally retarded'.

'There are probably between 4,000 and 5,000 children in Victoria who could be brought under the provisions of the [Mental Deficiency] Act when it is proclaimed. At present only about one-tenth are being dealt with by the Department of Mental Hygiene. That does not include the even larger number who are only dull or backward, and will still, as previously mentioned, be under the control of the educational authorities. Certain other departments and non-departmental institutions are at present handling more mentally deficient cases than they ought. It is almost a scandal the number of retarded children who enter some of the institutions of the Children's Welfare Department. There they are apt to stick.'

Recent investigations including the 'Forgotten Australians' inquiry have confirmed Springthorpe's view that children defined as mental defectives were indeed 'apt to stick' in children's institutions. Furthermore, the classification of many children as mentally deficient or retarded was often false. In many cases, the characteristics displayed by children were often the result of abuse and neglect, sometimes from the very institutions supposed to be 'caring' for them.

The book, Dolly Stainer of Kew Cottages (1996) tells the story of a woman falsely labelled an 'imbecile of poor grade' at the age of four in 1915 and subsequently spending her childhood in institutions at Kew.

Many submissions to Forgotten Australians mentioned the distress and offence felt by 'care' leavers who, upon accessing their records as adults, encountered descriptions of their childhood selves that included terms like 'idiot' or 'high grade mental defective'.

'I found out a lot from that file ... more than I really wanted to know. That's how I found out that I was classified as being 'high grade mental defective' and sent to 'homes' for mentally retarded boys [Submission No 94].'

'I was brought up in the Neerkol Orphanage outside Rockhampton from the age of 10 months to 12 years old. During this time I suffered mental, physical and sexual abuse from employees of Neerkol. I was treated as being mentally retarded from the age of two until the age of 10 when they discovered that all that was wrong with me was a simple tongue tie. [Submission No 218]'

The Forgotten Australians report included another story from a person admitted to Marillac House, an institution for people with intellectual disabilities, despite her having been classified by a psychologist as being 'clearly of normal intelligence'.

The support group Broken Rites, many of whose clients suffered abuse in training centres run by the St John of God Brothers, contend that

'Many SJOG inmates, especially wards of state, had behavioural or learning difficulties and were not necessarily born with an intellectual disability, although they certainly became educationally disadvantaged through their incarceration at St John of God.'